Pathological Findings in Koala Retrovirus-positive Koalas (Phascolarctos cinereus) from Northern and Southern Australia

Fabijan, J.; Sarker, N.; Speight, N.; Owen, H.; Meers, J.; Simmons, G.; Seddon, J.; Emes, R. D.; Tarlinton, R.; Hemmatzadeh, F.; Woolford, L.; Trott, D. J.

Abstract

© 2020 Elsevier Ltd Koala retrovirus (KoRV) infection shows differences in prevalence and load between northern and southern Australian koala populations; however, the effect of this on diseases such as lymphoma and chlamydial disease is unclear. This study compared clinicopathological findings, haematology and splenic lymphoid area of KoRV-positive koalas from northern (Queensland [Qld], n = 67) and southern (South Australia [SA], n = 92) populations in order to provide further insight into KoRV pathogenesis. Blood was collected for routine haematology and for measurement of KoRV proviral load by quantitative polymerase chain reaction (qPCR). Plasma samples were assessed for KoRV viral load by reverse transcriptase qPCR and conjunctival and cloacal swabs were collected for measurement of the load of Chlamydia pecorum (qPCR). During necropsy examination, spleen was collected for lymphoid area analysis. Lymphoma was morphologically similar between the populations and occurred in koalas with the highest KoRV proviral and viral loads. Severe ocular chlamydial disease was observed in both populations, but urinary tract disease was more severe in Qld, despite similar C. pecorum loads. No associations between KoRV and chlamydial disease severity or load were observed, except in SA where viral load correlated positively with chlamydial disease severity. In both populations, proviral and viral loads correlated positively with lymphocyte and metarubricyte counts and correlated negatively with erythrocyte and neutrophil counts. Splenic lymphoid area was correlated positively with viral load. This study has shown further evidence for KoRV-induced oncogenesis and highlighted that lymphocytes and splenic lymphoid tissue may be key sites for KoRV replication. However, KoRV infection appears to be highly complex and continued investigation is required to fully understand its pathogenesis.

Citation

Fabijan, J., Sarker, N., Speight, N., Owen, H., Meers, J., Simmons, G., Seddon, J., Emes, R. D., Tarlinton, R., Hemmatzadeh, F., Woolford, L., & Trott, D. J. (2020). Pathological Findings in Koala Retrovirus-positive Koalas (Phascolarctos cinereus) from Northern and Southern Australia. Journal of Comparative Pathology, 176, 50-66. https://doi.org/10.1016/j.jcpa.2020.02.003

• Journal Article Type: Article
• Acceptance Date: Feb 3, 2020
• Online Publication Date: Mar 12, 2020
• Publication Date: Apr 1, 2020
• Deposit Date: Feb 10, 2020
• Publicly Available Date: Mar 13, 2021
• Journal: Journal of Comparative Pathology
• Print ISSN: 0021-9975
• Electronic ISSN: 1532-3129
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 176
• Pages: 50-66
• DOI: https://doi.org/10.1016/j.jcpa.2020.02.003
• Keywords: Pathology and Forensic Medicine; General Veterinary
• Public URL: https://nottingham-repository.worktribe.com/output/3938368
• Publisher URL: https://www.sciencedirect.com/science/article/abs/pii/S0021997520300189?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: Pathological Findings in Koala Retrovirus-positive Koalas (Phascolarctos cinereus) from Northern and Southern Australia; Journal Title: Journal of Comparative Pathology; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.jcpa.2020.02.003; Content Type: article; Copyright: © 2020 Elsevier Ltd. All rights reserved.